The c class is a good car, design-wise and it's not too bad performance-wise either, but I always thought the C class appeals to a slightly different side of the market, people who do like a little sportiness in their ride, but ultimately place comfort and reliability as the primary things they look for in a car.
The 3 series in contrast has stronger emphasis on sportiness and overall performance. It allows for practical daily use (the sedan version anyway) but it is car that lets you have more fun than a C class.
So all these reviews are nice to read, but won't really change things. People who like C class will continue to buy C class, and those that like the 3 series will continue buying the 3 series.